Considering NAMOR is a large size, and is having boots made with few real seams for them to join several pieces together, I imagine it'd just be that Vass is using larger shells, which have lower quality areas within them? It was ordered and delivered as shell, sounds like an honest mistake/material defect rather than something malicious.

1. Vass only uses Horween Shell Cordovan.
2. Horween and other tanneries do sell horsehide, but Vass has not purchased any.
3. There were issues with recent lighter shades and Vass stopped selling those for now, and stands behind the shoes/boots made with that shell if there are issues.
4. The shell comes in multiple sizes, and the larger ones are required for boots. Latest shipment only had smaller pieces.
5. "Colorless" shell is available which can be "painted" by hand, but Vass is not doing that.
6. Vass only uses neutral wax and polish over the tanned shell. Some others use additional colored products.

how do you explain @NAMOR's boots that are clearly not shell and were sold as shell?